This invention pertains to fabrication of electronic devices such as integrated circuits; more specifically, this invention relates to methods and formulations for cleaning substrates having cap layers containing at least one of the chemical elements cobalt and nickel on metal and dielectric damascene metallization structures.
Cleaning of surfaces having heterogeneous compositions is challenging. This is particularly true in situations such as for surfaces that are subject to corrosion and such as surfaces having different corrosion rates for the heterogeneous compositions. The problem is greater still for surfaces having thin film layers such as layers used in fabricating electronic devices. For electronic device fabrication, surfaces having films around 20 nm thick need to be cleaned while avoiding degradation of the surface quality and thickness of the films.
In a specific case, a metal cap is applied to copper interconnects that are embedded in a dielectric structure to form a damascene metallization layer. In order to provide good electrical performance such as low leakage current with good yield, high breakdown voltage and time dependent dielectric breakdown, the surface of the metal cap and the surface of the dielectric area are preferably cleaned so as to remove contaminants and defects. During this treatment, the metal cap should not suffer significant metal loss, or experience pitting or other forms of localized corrosion. Examples of materials for the metal cap are materials such as cobalt, cobalt alloy, cobalt-nickel alloy, nickel, and nickel alloy. In addition, defects such as particles and residues have to be removed from the entire wafer.
There is a need for cleaning solutions and methods of cleaning substrates that can be used to fabricate electronic devices. More specifically, there is a need for improved solutions and methods that can meet the requirements for such devices.